1. Field of the Invention
The present invention relates to a battery pack structured with plural battery modules each of which is constituted by plural unit cells arranged in a row. More particularly, it relates to a battery pack with a spacer which intervenes and constitutes a cooling medium passage for flowing cooling medium between adjoining battery modules.
2. Description of Related Art
There has conventionally been known a battery pack structured such that plural unit cells are integrated in the battery pack and cooling medium flows between adjoining unit cells. For example, Japanese Unexamined Patent Publication (Kokai) No. 2000-251954 discloses a battery pack like that. In this battery pack, plural unit cells are arranged and cooling medium passages (cooling passages) are arranged at both sides in relation to direction the unit cells are arranged. Significant number of protrusions are provided on adjoining wall surfaces of adjoining battery jars (battery cases) and made to contact with each other, whereby the cooling medium passages are formed between the adjoining wall surfaces. A lid body is provided on the battery pack, and there are formed an inlet orifice for supplying the lid body cooling medium and an outlet orifice for exhausting cooling medium (see FIG. 1 and corresponding description portion of Japanese Unexamined Patent Publication (Kokai) No. 2000-251954). In such a battery pack, cooling medium supplied from the inlet orifice is flowed in the cooling medium passage and exhausted from the outlet orifice. When flowing, the cooling medium touches those battery jars and cools down the unit cells flowing in an up-and-down direction of each unit cell (a direction orthogonal to a row direction of the unit cells).
Other than the above publication, Japanese Unexamined Utility Model Publication (Kokai) No. H5(1993)-90816, Japanese Unexamined Patent Publication (Kokai) No. 2000-182582, Japanese Unexamined Patent Publication (Kokai) No. 2001-35548, and Japanese Unexamined Patent Publication (Kokai) No. H10(1998)-3950 disclose the related art.
The battery pack directed to Kokai No. 2000-251954 is structured such that cooling medium is flowed in an up-and-down direction of each unit cell for cooling down each unit cell. Therefore, the lid body is provided on a top portion of the battery pack and the passage for flowing the cooling medium is provided between the top portion of the unit cell and the lid body. Since height of the battery pack becomes taller by just much of providing the passage on the top portion of the battery pack, shortening of the battery pack cannot be realized.
Furthermore, unit cells arranged on inlet orifice side are cooled down by cooling medium in low temperature state. However, since the cooling medium becomes warmer as flowing in the cooling medium passage, unit cells on outlet orifice side are cooled down with warm cooling medium. That is, unit cells on inlet orifice side are well cooled down while unit cells on outlet orifice side are not cooled down as much as inlet orifice side. Therefore, cooled-down state is not uniform by each unit cell.
Kokai No. H10(1998)-3950 considers relation of cooling medium and batteries for cylindrical batteries to be integrated in a battery pack. However, there is no need to consider a problem on expansion of battery jars with reference to cylindrical batteries, which means technical thought is quite different.